Spring-operated constant torque transmission for electric clocks



Dec. 27, 1966 PFEFFER SPRING-OPERATE ONSTANT TORQUE TRANSMISSION FOR ELECTRIC CLOCKS 2 Sheets-Sheet 1 Filed Dec. 10, 1964 N H \w [9N I W 131?? 11$ f x m I5 7 l 8 ya INXJENTOR.

( av e 7er Dec. 27, 1966 v. PFEFFER 3,294,198 I SPRING-OPERATED CONSTANT TOR TRANSMISSION FOR ELECTRIC CLO Filed Dec. 10, 1964 2 Sheets-Sheet 2 INVENTOR.

V Viz/emf We /76F Maw/ W! ilnited States Patent Gfifice 3,294,198 Patented Dec. 27, 1966 3,294,198 SPRING-OPERATED CONSTANT TORQUE TRANS- MISSION FOR ELECTRIC CLOCKS Vaclav Pfelfer, Prague, Czechoslovakia, assignor to liabofziitorni Pristroje, narodni podnilr, Prague, Czechos ova a Filed Dec. 10, 1964, Ser. No. 417,384 Claims priority, applicationlCzechoslovakia, Jan. 6, 1964, 8 4

4 Claims. (Cl. 185-37) This invention relates to clocks, and particularly to a winding barrel arrangement for transmitting torque from a power source, such as an electric motor, to the clockwork mechanism proper.

An object of the invention is the provision of a transmission, including a winding barrel, which has a constant output torque regardless of irregular operation, and even temporary stoppage of the motor which furnishes primary operating power.

Another object is the provision of a transmission of the type described which avoids the use of ratchets and the operating noise of such devices.

A further object is the provision of a very simple constant torque transmission for operating a clockwork or the like.

With these and other objects in view, as will hereinafter become apparent, the transmission of this invention may include a barrel and a shaft coaxially and rotatably mounted on the barrel. A spiral spring is interposed between the barrel and shaft in such a manner that it winds and unwinds with corresponding changes in the spring stress when the barrel and shaft rotate relative to each other. A clutch normally connects a driving wheel to the shaft in response to rotation of the latter in a predetermined direction by a motor whereby the spring is wound.

,The clutch is disengaged by a control device in repsonse to a predetermined minimum stress of the spring during the rotation of the driving Wheel, and the control device causes the barrel to be locked to the driving wheel when the shaft and barrel have been rotated relative to each other under the driving force of the spring through a number of revolutions greater than one while the driving wheel stands still.

Other features, additional objects, and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of a preferred embodiment when considered with the attached drawing in which:

FIG. 1 shows a constant torque transmission of the invention in section on the axis of its winding barrel; and

FIG. 2 illustrates the apparatus of FIG. 1 in a fragmentary axial end view.

Referring now to the drawing in detail, there is seen a barrel consisting of a gear Wheel 1, a short cylindrical drum 2 coaxial and integral with the wheel 1, and a cover 4 releasably attached to the drum 2 for closing the barrel cavity which holds a leaf spring 3 wound into a spiral. The two ends of the spiral spring 3 are respectively attached to claws 6, 7 on the drum 2 and on a shaft which is received in respective openings of the wheel 1 and the cover 4 for free rotation about the barrel axis. An enlarged portion of the shaft in the barrel cavity prevents axial movement of the shaft 5 when the barrel is closed. The shaft 5 is journaled in bearing portions 22, 23 of a supporting structure, not otherwise shown, and carries the barrel.

An arbor 8 is journaled in the cover 4 for rotation about an axis parallel to that of the shaft 5, but radially spaced from the same. The tubular hub 10 of a Maltese cross cam 9 is mounted on the arbor 8 and secured thereon by a spring clip 12. A radial arm 11 is axially spaced from the earn 9 on the hub 10, and integral with the hub and cam.

A bushing 16 is fixedly mounted on the portion of the shaft 5 adjacent the outer face of the cover 4 and has a fixed flange 15. An axial pin 13 fastened near the periphery of the flange 1S and a shoulder 14 on the bushing 16 cooperate with the Maltese cross cam 9 in a conventional manner to turn the cam through a quarter of a turn once during each revolution of the bushing 16.

The cylindrical hub 18 of a toothed drive wheel 17 is rotatably mounted on the shaft 5 and is secured axially adjacent the bushing 16 by a spring clip 19. A helical spring 20 envelops respective coaxial cylindrical face por tions of the bushing 16 and of the hub 17 which have the same diameter and are axially adjacent each other. One end of the spring 20 is fastened in a recess of the shoulder 14, the other end 21 is bent radially outward from a portion of the hub 18 adjacent the wheel 17, and thence axially toward the cover 4 and into the path of the arm 11.

The wheel 17 meshes with the pinion 24 of an electric motor, not otherwise shown, which will be understood to be equipped with a unidirectional clutch preventing backward rotation of its rotor by the spiral spring 3.

The afore-described apparatus transmits torque from the pinion 24 to a non-illustrated device, such as the hands of a clock, connected to the barrel by meshing engagement with the gear wheel 1, in the following manner.

The pinion 24 continuously turns the drive wheel 17 clockwise, as viewed in FIG. 2, as long as the non-illustrated, associated motor is energized. The resulting relative rotation of the wheel 17 and of the shaft 5, initially assumed to stand still, causes the helical spring 20 to be tightened about the hub 18 and the bushing 16 as long as the arm 11 does not abuttingly engage the end portion 21 of the spring 20, FIG. 2 illustrating a position of the spring just short of engagement with the arm 11.

The spring 20, in cooperation with the bushing 16 and hub 18, thus forms a clutch which couples the drive wheel 17 to the shaft 5 when engaged, whereby the spring 3 is wound until its tension is sufficient to overcome the resistance of a load applied to the gear wheel 1, such as the frictional resistance of the connected portion of a clockwork mechanism, not itself shown.

If'the pinion 24 moves at a speed precisely corresponding to the speed of the gear wheel 1, the relative position of all parts of the transmission remains the same. If the pinion 24 rotates faster than at the corresponding speed, as is preferred in normal operation, the end portion 21 of the spring 20 is moved against the arm 11 and stopped thereby, so that further rotation of the wheel 17 at a speed greater than that of the barrel 1, 2, 4 causes the spring 20 to be loosened, permitting the hub 18 to slip. Torque is transmitted from the pinion 24 to the shaft 5 through the slipping clutch 16, 18, 29. Excess energy stored in the spring 3 during fast movement of the pinion 24 while the clutch was engaged is released at this stage through the gear wheel 1 to the connected load, thereby moving the arbor 8 away from the spring end 21 to restore the original relative position of the transmission elements.

This cycle is repeated as long as the pinion 24 moves at a higher speed than that corresponding to the output speed of the gear wheel 1 which may be determined by the connected clockwork mechanism in a conventional manner. The transmission provides a source of substantially constant torque, the cyclic deviations of the torque from precise uniformity being determined by the characteristics of the clutch 16, 18, 20, and those of the spring 3, and capable of being held to a minimum. The spring 3 particularly is effective in holding the output torque of the transmission practically constant.

In the event of power failure or other stoppage of the pinion 24, the spring 3 operates as a temporary power source by unwinding while the shaft 5 is held stationary by the clutch 16, 18, 20 and the afore-mentioned nonillustrated unidirectional clutch in the motor attached to the pinion 24.

Relative rotation of the shaft 5 and the barrel 1, 2, 4, is not impeded by abutting engagement of the arm 11 and the spring end 21 while the barrel makes four revolutions on the shaft 5. The arm 11 is swung out of the path of the spring end 21 by the Maltese cross cam 9 during the initial half turn of the barrel, and is not placed again into the path of the arm 11 until the barrel has made four turns. The arm 11 then strikes the end 21 of the spring 20, and thereby stops the gear wheel 1, ultimately locking the barrel to the driving wheel 17. Unwinding of the spring 3 during emergency operation of a connected clockwork during a power failure is thus limited to a period in which the spring 3 may readily be designed to operate at constant torque. When this period passes without restoration of electric power to the pinion 24, the clock is stopped.

The transmission of the invention thus can bridge short periods of power failure without significant change in output torque, but cannot cause erroneous readings on an attached clock by running down of the spring 3 until its output torque declines to a significant extent.

If power is restored to the pinion 24, reserve energy is again quickly stored in the spring 3. As long as the full tension of the spring 3 is not restored, the shaft 5 and barrel 1, 2, 4 rotate relative to each other, and the Maltese cam 9 rotates the arm 11 until it engages the spring 21 and temporarily disengages the clutch 16, 18, 20. The apparatus thereby reverts to the normal cycle of operation, as initially described. The spring 3 is restored to its normal initial state of tension.

The illustrated transmission thus provides constant drive torque for an attached apparatus, such as a clockwork, and provides standby power for operation of the apparatus during temporary power failures, important features in the operation of electric clocks. The transmission of the invention replaces more complicated known constant torque devices and standby power sources.

It should be understood, of course, that the foregoing disclosure relates only to a preferred embodiment of the invention, and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What I claim is:

1. A spring-operated source of constant torque comprising, in combination:

(a) a barrel member having an axis;

(b) a shaft member mounted on said barrel member for rotation about said axis;

() a spiral spring operatively interposed between said members for winding and unwinding thereof and for corresponding changes in the stress of said spring when said members rotate relative to each other;

(d) a driving wheel;

(e) means for rotating said wheel in a predetermined direction;

(f) clutch means normally responsive to rotation of said driving wheel in said direction for drivingly connecting the same to one of said members and for thereby winding said spring; and

(g) clutch control means operative to disengage said clutch means in response to a predetermined minimum stress of said spring while said driving wheel is rotated in said direction, and to lock the other one of said members to said driving wheel in response to relative rotation of said members under the driving force of said spring through a number of revolutions greater than one, when said driving wheel stands still.

2. A source as set forth in claim 1, wherein a portion of said clutch means is secured to said one member for rotation therewith, and said clutch control means include abutment means on said portion and on said other member respectively, and moving means for moving one of said abutment means toward and away from a position of engagement with the other abutment means in response to relative rotation of said members.

3. A source as set forth in claim 1, wherein said driving wheel is rotatably mounted on said shaft member and has an axially extending face about said axis, said clutch means including a helical spring extending about said axis and normally frictionally engaging said face, one end portion of said helical spring being fastened to said shaft member for tightening of said spring about said face when said driving wheel rotates in said direction relative to said shaft member, the other end portion of said helical spring extending radially outward from said axis, and said clutch control means including a stop member mounted on said barrel member and moving means responsive to said relative rotation of the barrel member and the shaft member under the driving force of said spiral spring for moving said stop member relative to said barrel member toward and away from an operative position in which the stop member engages said other end portion of the helical spring when said barrel member and said shaft member rotate relative to each other.

4. A source as set forth in claim 3, wherein said moving means include a Maltese cross cam mounted on said barrel member for rotation about an axis spaced from the axis of said barrel member, and cooperating engaging means on said shaft member for turning said cam, said stop member being mounted on said cam.

References Cited by the Examiner UNITED STATES PATENTS 1,022,087 4/1912 Jenney -40 1,332,870 3/1920 Gill 18540 1,562,051 11/1925 Powers 185--40 1,799,454 4/ 1931 Burke 58-82 2,318,453 5/1943 Bernard 18540 2,614,672 10/1952 Launder l92l50 2,759,561 8/1956 Bolsey 18540 2,933,882 4/1960 Sonobe et al 5838 EDGAR W. GEOGHEGAN, Primary Examiner.

GERALD F. BAKER, Examiner. 

1. A SPRING-OPERATED SOURCE OF CONSTANT TORQUE COMPRISING, IN COMBINATION: (A) A BARREL MEMBER HAVING A AXIS: (D) A SHAFT MEMBER MOUNTED ON SAID BARREL MEMBER FOR ROTATION ABOUT SAID AXIS; (C) A SPIRAL SPRING OPERATIVELY INTERPOSED BETWEEN SAID MEMBERS FOR WINDING AND UNWINDING THEREOF AND FOR CORRESPONDING CHANGES IN THE STRESS OF SAID SPRING WHEN SAID MEMBERS ROTATE RELATIVE TO EACH OTHER; (D) A DRIVING WHEEL; (E) MEANS FOR ROTATING SAID WHEEL IN A PREDTERMINED DIRECTION; (F) CLUTCH MEANS NORMALLY RESPONSIVE TO ROTATION OF SAID DRIVING WHEEL IN SAID DIRECTION FOR DRIVINGLY CONNECTING THE SAME TO ONE OF SAID MEMBERS AND FOR THEREBY THE SAME TO ONE OF SAID MEMBERS AND FOR (G) CLUTCH CONTROL MEANS OPERATIVE TO DISENGAGE SAID CLUTCH MEANS IN RESPONSE TO A PREDETERMINED MINIMUM STRESS OF SAID SPRING WHILE SAID DRIVING WHEEL IS ROTATED IN SAID DIRECITON, AND TO LOCK THE OTHER ONE OF SAID MEMBERS TO SAID DRIVING WHEEL IN RESPONSE TO RELATIVE ROTATION OF SAID MEMBERS UNDER THE DRIVING FORCE OF SAID SPRING THROUGH A NUMBER OF REVOLUTIONS GREATER THAN ONE, WHEN SAID DRIVING WHEEL STANDS STILL. 